I'm a bit embarrassed to ask this, but, my dictionary lists some nouns as "plural" after giving the usual nominative and genitive singular of the noun in the entry. Does this mean that the singular declensions work as plural? Another question I have is, do proper nouns ordinarily have plural declensions?

I'm trying a method where you learn all of the declensions and conjugations before doing anything else. I started with the Wheelock vocab, but got bored and started getting nouns from my Cassell's dictionary. Now I'm slowing myself down worrying about this plural business. Every study session seems to get half lost in things like this.

Could you provide an example? I have Cassell's but can't recall ever seeing what you've described.

As for proper nouns, many cities and towns, such as Athenae and Tarquinii, are plurale tantum words, i.e. grammatically plural but singular in meaning. Names of persons can be pluralized by regular declension if the need arises. Caesares, referring to the imperial title, is the most salient example.

where the noun in the singular has a different meaning than the noun in the plural? For instance, Cassell's gives the following entry for ops, opis (f.):

ops, opis, f., plur., opes, -um...

Where, for instance, ops generally means "aid, help, support, assistance" or "power, might, strength, influence," and so forth in the singular, but more often means "wealth, riches, resources, might, power" in the plural?

Yes! I think that's it, that last example using "letter" and "letters". Thanks! I'm still a bit confused about proper nouns, but I'm going to go over the replies more carefully before asking. This site's a really good idea; there's always some little stumbling block like this that can derail a study session, if there's no one to ask.

A full column or more, more than 50 citationsB half column, more than 20 citationsC more then 5 citationsD 4-5 citationsE 2-3 citationsF only 1 citation type FREQUENCY_TYPE is ( -- For dictionary entries X, -- -- Unknown or unspecified A, -- very freq -- Very frequent, in all Elementry Latin books B, -- frequent -- Frequent, in top 10 percent C, -- common -- For Dictionary, in top 10,000 words D, -- lesser -- For Dictionary, in top 20,000 words E, -- uncommon -- 2 or 3 citations F, -- very rare -- Having only single citation in OLD or L+S I, -- inscription -- Only citation is inscription M, -- graffiti -- Presently not much used N -- Pliny -- Things that appear only in Pliny Natural History );For inflections, the same type is used with different weights